Process for cooking vegetable fiber



Patented Apr. 26, 1927.

UNITED STATES SIDNEY D. WELLS, OF QUINCY,

PROCESS FOR COOKING VEGETABLE FIBER.

No Drawing.

This invention relates to processes for softening vegetable fibrousmaterial, such as wood, cereal straws, and grasses, whereby aren'iarkably fine product may be obtained by the use of relativelyinexpensive chemicals.

The process includes the use of sodium carbonate and sulphur and isconducted under such conditions that these materials combine and effectdesired changes in the fibrous ma terial such-as heretofore have beenobtainable only by the use of more expensiv chemicals. The resultantpaper or paper board produced from materials obtained by this process ismore pliable and stronger than that ordinarily obtainable from straw,for example, by other methods such as give yields above fifty or sixtyper cent. Under the microscope, the fibers give the color reactionscharacteristic of well cooked pulp obtainable by the sulphate processand which is c011- sidercd a much finer product than the usual strawpulps such as are obtained in cooking straw with lime. The cheapness ofthe cooking reagents proposed as result of this present invention andthe quality of the product makes possible the more complete utilizationof straw.

In conducting the process, the cooking vessels, digestors, are chargedwith straw or other vegetable fibrous material in the usual I mannertogether with about seven pounds sodium carbonate, one pound of sulphur,and twenty-five gallons of water for each one hundred pounds dry weightof straw. A

cooking treatment of six hours is suflicient if at least five andone-half hours are at a temperature of 145 C. The action is conducted inclosed vessels, and of course at itl pressures greater than atmosphericpressure.

After digestion, the stock is dumped,

washed, and beaten in accordance with any ofthe methods practiced in theart and such subsequent steps form no part of the present inventlon.

Sulphur will not combine with sodium carbonate at the temperature of100. C. or below, but in practicing the present invention, it has beenfound that if these materials are heated to temperatures ofapproximately 120 ,C. or above in the presence of water and vegetablefibrous material, the cooking effect approximates that obtained whensodium sulphide or h drosulphide is used,

and a softened material is obtained which may be converted to paper orpaper board Application filed June 29,

1926. Serial No. 119,471.

products using the usual methods. Under the conditions of the cookinsodium is weakly ionized to Na and HC 3 ions. The Na ions probably actin conjunction with OH ions from the water on the sulphur and the sameions are formed that occur when sodium sulphide is dissolved in water.

The chemicals may be combined in rotary digestors in the presence ofstraw and water or by suitable mechanical means before being introducedinto the digestors.

Heretofore, it has been proposed to use sulphur with soda ash and underconditions in which the sulphur is used as a colloidal material as animportant feature and under temperature conditions at which there is nochemical combination between the sulphur and the soda ash. The presentprocess in contrast to such prior uses depends on the softening actionproduced when these materials combine as effected by heating in thepresence of vegetable fibrous material. It is believed to be new to usesulphur compounds in the manner described and claimed.

Sulphur has also previously been used in combination with caustic sodaand also in combination with lime. The result of the first would be theformation of caustic soda and sodium sulphide, simulating a modificationof the soda process and not relying on the use of sodium carbonate asthe softening agent, as in the present invention. vVhere lime has beenused with sulphur, theproducts formed are different from those of thepresent process, and in one use, it has been necessary to supplementsuch materials with sodium carbonate used, not as a cooking agent, butas an eliminator for undesirable products formed in the digestion whenlime and sulphur are present.-

Claims to the use of sodium carbonate and sulphur compounds andemphasizing the avoiding of causticizing are embodied in my pendingapplication, Serial No. 137,819, filed- September 25, 1926. V

I claim 1. In a process of softening ve etable fibrous material, thesteps consisting o treatwith a solution of sodium carbonate and sulphur,and under temperature conditions of at least 120 C. I

4:. In a process of softening vegetable fibrous material, the stepsconsisting of treating such fibrous material with a solution of sodiumcarbonate and sulphur in proportions of approximately seven parts of thecarbonate to one art of sulphur for each one hundred parts 0 fibrousmaterial.

5. In a process of softening vegetable fibrous material, the stepsconsisting of treating such fibrous material with a solution of sodiumcarbonate and sulphur in proportions of approximately seven parts ofcarbonate to one part of sulphur and with two hundred parts of water foreach one hundred parts of vegetable fibrous material.

'6. In a process of softening vegetable fibrous material, the stepsconsisting of treating such fibrous material in a closed vessel with asolution of sodium carbonate and sulphur in proportions of approximatelyseven parts of carbonate to one part of sulphur and with two hundredparts of water for each one hundred parts of vegetable fibrous materialand under temperature conditions of approximately 145 C. maintained fora period of at least five and one-half hours.

7. In a process of softening vegetable fibrous material, the stepsconsisting of treating such fibrous material in a closed vessel andunder pressure greater than atmospheric ressure and with a solution ofsodium caronate and sulphur and under temperature conditions ofapproximately 145 C. main: tained for at least five and one-half hours.

8. In a process of softening vegetable fibrous material, the stepsconsisting of mixing a water solution solelyof sodium carbonateand'sulphur and cooking vegetable fibrous material with such a resultantmixture and thereby softening the fibrous material.

In testimony whereof I affix my signature.

SIDNEY D. WELLS.

